<!doctype html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
        content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style>
      body {
          padding: 0;
          margin: 0;
      }

      #app {
          margin: 30px;
          width: 80px;
          height: 100px;
          background-color: rosybrown;
      }
  </style>
</head>
<body>
  <div id="app"></div>

  <script>
    // Element
    const app = document.querySelector("#app")
    console.dir(app)

    // clientWidth/clientHeight

    // style: {"width": "100px"}


    const body = document.querySelector("body")
    console.dir(body)
    }

  </script>
</body>
</html>
